/Engine/Source/Developer/TargetPlatform/Public/Interfaces/ITargetPlatform.h
Gets an integer representing the height fog mode for opaque materials on a platform.
0 if no override (i.e. use r.VertexFoggingForOpaque from project settings); 1 if pixel fog; 2 if vertex fog.
int32 GetHeightFogModeForOpaque() const